As a related-art heat exchanger, there is known a heat exchanger including a heat exchanging unit including a plurality of stages of refrigerant flow passages allowing refrigerant to flow in from end portions on one side thereof and flow out of end portions on the other side thereof that are juxtaposed to the end portions on the one side, and a distributing and joining unit connected to the heat exchanging unit and including a distributing flow passage allowing the refrigerant to be distributed and flow out, and a joining flow passage allowing the refrigerant to be joined and flow out (for example, see Patent Literature 1).